Method for forming an integral electromagnetic radiation shield in an electronic package

ABSTRACT

A method and system for fabricating an integral electromagnetic radiation shield for an electronic package is disclosed. Various embodiments include exposing a portion of at least one ground contact feature in an electronic package by removing a portion of the electronic package above the at least one ground contact feature to form at least one trench above the at least one ground contact feature; depositing electromagnetic radiation shield material in the at least one trench to substantially fill the at least one trench with a trench deposit; and depositing additional electromagnetic radiation shield material over a substantial portion of the electronic package, wherein the electromagnetic radiation shield material in the trench and over the substantial portion of the electronic package form an integral electromagnetic radiation shield which is electrically connected to the at least one ground contact feature.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/315,903, filed on Dec. 22, 2005 now U.S. Pat. No. 7,626,247, which isincorporated herein by reference in its entirety.

FIELD

The subject matter of the present invention relates to electronicspackaging and more particularly to a method and system for fabricatingan integral electromagnetic radiation shield in an electronics package.

BACKGROUND

Conventional electronics used in certain applications emit highfrequency electromagnetic radiation that can interfere with theperformance of other devices. For example, conventional microelectronicradio frequency (RF) devices emit RF radiation. RF radiation mayadversely affect the performance of other electronic components, such ascertain molded array packages (MAPS) or other semiconductor packages,used in conjunction with the conventional microelectronic RF device.

In order to protect other conventional electronic components from RFradiation, an electromagnetic radiation shield is provided between theconventional microelectronic RF device and other conventional electroniccomponents. Typically this is performed by surrounding the otherconventional electronic components with a physical shield. The physicalshield is typically composed of an electrically conductive metallicmedia. For example, a conventional metal cover may be provided for eachconventional electronic component desired to be shielded. In someconventional electronic components, the metal cover might includethrough holes that facilitate placement of mold compound that might beused as a protective layer for the underlying electronic device.

Although conventional metal shields can reduce the interference due tothe RF radiation, one of ordinary skill in the art will readilyrecognize that such conventional metal covers are costly to fabricate.Typically, such conventional metal shields are custom designed forindividual conventional electronic components. In addition, customassembly equipment is typically used for assembling the conventionalmetal cover and attaching the conventional metal cover to the component.The custom assembly and design are typically expensive.

In addition, the conventional metal cover may also increase the size ofthe conventional electronic component being shielded. This increase inthe size of the conventional electronic component may result in anincrease in size of the final product employing the conventionalelectronic component. Typically, such an increase in size isundesirable. Consequently, use of conventional metal covers may becostly and undesirable for other reasons.

SUMMARY

The subject matter of the present invention provides a method and systemfor fabricating a shield for an electronics package. The subject matterof the present invention may be applied to various types of organic andinorganic substrate based electronics packages. The typical package typeis a Molded Array Package (MAP). The electronics package includes asubstrate, at least one ground contact feature, and a protective layer.The electronics package is physically coupled to at least one additionalelectronics package through at least the substrate. The method andsystem comprise exposing a portion of the at least one ground contactfeature, preferably during a singulation process. The exposing stepforms at least one trench above the at least one ground contact feature.The method and system also comprise depositing a metal shieldingmaterial that substantially covers the top surfaces and side surfaces ofthe electronics package, filling the trenches, and is electricallyconnected to the at least one ground contact feature on each electronicpackage substrate site.

According to the method and system disclosed herein, the presentinvention provides an integral RF shield that may be lower in cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart depicting a method for providing anelectromagnetic radiation shield in an electronics package in accordancewith an example embodiment of the present invention.

FIGS. 2-7 depict side views of a semiconductor package including anelectromagnetic radiation shield during fabrication in accordance withan example embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The subject matter of the present invention relates to electronicspackages utilizing electromagnetic shielding. The following descriptionis presented to enable one of ordinary skill in the art to make and usethe invention and is provided in the context of a patent application andits requirements. Various modifications to the preferred embodiments andthe generic principles and features described herein will be readilyapparent to those skilled in the art. Thus, the present invention is notintended to be limited to the embodiments shown, but is to be accordedthe widest scope consistent with the principles and features describedherein.

The subject matter of the present invention provides a method and systemfor fabricating an electromagnetic radiation shield for an electronicspackage. The electronics package includes a substrate, at least oneground contact feature, and a protective layer. The electronics packageis physically coupled to at least one additional electronics packagethrough at least the substrate. The method and system comprise exposinga portion of the at least one ground contact feature by removing aportion of the electronics package above the ground contact feature. Theexposing step forms at least one trench above the at least one groundcontact feature. The method and system also comprise depositing anelectromagnetic radiation shield that substantially covers theelectronics package, fills the at least one trench, and is electricallyconnected to the at least one ground contact feature. The method andsystem also comprise separating the electronics package from the atleast one additional electronics package such that a remaining portionof the electromagnetic radiation shield substantially enclosing aportion of the electronics package above the ground contact feature thatremains.

The subject matter of the present invention will be described in termsof particular components and particular electronics packages, such asMAPs. However, one of ordinary skill in the art will readily recognizethat other and/or additional components and other and/or additionalelectronics packages could be used. For example, the subject matter ofthe present invention may be applied to various types of electronicspackages that use a leadframe array or substrate array strip format suchthat each strip contains multiple repeat individual sites for packageassembly. In addition, the present invention is described in the contextof particular methods. One of ordinary skill in the art will, however,readily recognize that other methods having other and/or additionalsteps could be used.

FIG. 1 is a flow chart depicting one embodiment of a method 100 forproviding an electromagnetic radiation shield in accordance with thepresent invention in an electronics package. FIGS. 2-7 depict a sideview of one embodiment of an electronics package 210, a MAP, includingone embodiment of an electromagnetic radiation shield in accordance withthe present invention during fabrication. Referring to FIGS. 1-7, themethod 100 is described in the context of the MAP 210. However, one ofordinary skill in the art will readily recognize that the method 100 canbe used with other semiconductor packages. In addition, one of ordinaryskill in the art will readily recognize that the electromagneticradiation shield, described below, could be used with othersemiconductor packages.

FIG. 2 depicts the substrate strip 200 including the MAP 210 prior tofabrication of one embodiment of the electromagnetic radiation shield inaccordance with the present invention. In forming the MAP 210, multipleelectronic dice and/or other components are attached and electricallyconnected to each site on the leadframe array or substrate array first,mass over-molded and then singulated into individual electronic packagessuch as the MAP 210. The substrate strip 200 shown thus includes asubstrate 202, ground contact features 204 and 206, and a protectivelayer 208. The MAP substrates 202 are typically fabricated with anorganic substrate core material, such as polyamide, BT resin or FR-4,FR-5 material. The circuitry metal for these substrates 202, such as forground contact feature 204 and 206, is typically copper. Thesesubstrates can have metal circuitry on both sides of the organic core,multi-layer metal (4, 6, 8 or more metal layers are also used).

A solder mask layer (not shown), typically made with an epoxy basematerial, coats both top and bottom metal layers exposing the bond padregions (not shown) and or component attach regions (not shown) on thetop and solderball attach regions (not shown) at the bottom of thesubstrate strip 200. The exposed metal is over-plated with typicallynickel and gold metal to facilitate wire bonding and soldering. Theground contact features 204 and 206 may have a variety of shapes such asa pad, a line, or a frame. However, ground contact features 204 and 206are depicted as ground planes. In addition, the ground planes 204 and206 are preferably designed to be at the extreme external edge of theindividual electronic package substrate site. During the MAP packagingassembly process, discrete components (not shown), if present, are firstattached to the individual package substrate sites of the substratestrip 200 by soldering or epoxy.

The dice (not shown) and/or components (not shown) are attached toindividual sites and wirebonded or flip-chip soldered. The substratestrip is then overmolded using the protective layer 208. The protectivelayer 208 is typically an epoxy mold compound. Consequently, the MAP 210is physically coupled to additional MAPs 210′ and 210″ through at leastthe substrate 202. In the embodiment shown, the MAP 210 is coupled tothe MAPS 210′ and 210″ through the substrate 202, the ground planes 204and 206, respectively, and the protective layer 208. As discussed above,in the embodiment shown, in which the electronics package 210 beingfabricated is a MAP, the protective layer 208 is an over-mold compound.Thus, in one embodiment, the protective layer 208 includes an epoxy moldthat has been over-molded to the substrate 202. The MAP 210 alsogenerally includes other active and/or passive electronic componentsthat have been attached, bonded, and electrically coupled with portionsof the substrate 202. However, for simplicity, such electroniccomponents are not shown.

Referring to FIGS. 1 and 2, a portion of the ground planes 204 and 206are exposed by removing a portion of the electronics package above theground planes 204 and 206, respectively, via step 102. Step 102 istypically is performed during the singulation step, which is used toseparate the MAPs 210, 210′ and 210″. A saw or laser is preferably usedto perform the portion of the singulation in step 102. The saw or lasercuts through the total thickness of the protective layer 208 and stopsat the substrate strip's “top” surface exposing the ground planes 204and 206. In the embodiment shown, step 102 is preferably performed byutilizing a wide saw blade to cut into the MAP 210, stopping at theground planes 204 and 206. The wide saw blade is wider than a blade useto separate the packages. The typical range of widths for the saw bladeused to partially cut the MAP (i.e. used in step 102) is 0.002″ to0.010″ wider than the MAP singulation saw blade used in step 108.However, depending on the ground contact feature size design, the sawblade width can vary.

FIG. 3 depicts substrate the strip 200 including the MAP 210 during step102. Thus, the saw blade(s) 214 used in exposing the ground planes 204and 206 are shown. Note that in one embodiment a single saw blade 214 isused multiple times to make the cuts. FIG. 4 depicts the substrate strip200 including the MAP 210 after step 102 has been completed. Thus, theground planes 204 and 206 are exposed. In addition, the ground planes204 and 206 have not been cut through by the saw blades 214. Thus,trenches 216 and 218 above the ground planes 204 and 206, respectively,have been formed.

An electromagnetic radiation shield material is deposited, via step 104.Step 104 preferably includes conformally depositing a metallic materialover the surface of the devices 210, 210′ and 210″, particularlyincluding the protective layer 208 and ground planes 204 and 206. In oneembodiment, the metallic material includes materials such as Ni and/orFe. In another embodiment, the metallic material may be a metal-polymercomposite material. Various methods could be used to provide theelectromagnetic radiation shield. For example, in various embodiments,screen printing, spraying and curing, stencil printing, brushing, and/orvacuum depositing may be used to provide the electromagnetic shield.

FIG. 5 depicts substrate the substrate strip 200 including the MAP 210after step 104 has been performed. Thus, the electromagnetic shield 220has been deposited. The electromagnetic shield 220 substantially coversthe electronic package 210. In addition, the electromagnetic shield 210substantially fills the trenches 216 and 218. The electromagnetic shield210 is also electrically coupled with the ground planes 204 and 206. Theelectromagnetic shield 220 thus substantially covers the top surfacesand side surfaces of the MAP 210, filling all the saw/laser cut trenches216 and 218, and is electrically connected to the ground planes 204 and206 on each electronic package substrate site. Stated differently, thesubstrate strip may be completely coated with metal. However, as can beseen in FIG. 5, the MAPS 210, 210′, and 210″ are still physicallyconnected. In a preferred embodiment, after step 104 is performed,package solderballs (not shown), if used, may be attached to the bottomof the substrate strip.

The MAP 210 is separated from the additional MAPs 210′ and 210″, viastep 106. Thus, the singulation process is completed in step 106. Step106 is performed such that a remaining portion of the electromagneticradiation shield 220 still substantially encloses the portion of the MAP210 above the one ground planes 204 and 206. Stated differently, step106 is performed such that the electromagnetic shield 210 is stillcapable of functioning as a shield. The cut performed in step 106 may beperformed using a laser or a saw. The saw or laser is preferablyconfigured to cut through the mid-point of the trenches 216 and 218. Inthe embodiment shown, step 106 is performed using a saw blade that isthinner than the saw blade used in step 102. In addition, the saw bladewould cut through not only the shield 220, but also the ground planes204 and 206, as well as the substrate 202. Once the MAP 210 is separatedfrom the additional MAPs 210′ and 210″, any further fabrication of theMAP 210 may be completed.

FIG. 6 depicts the substrate strip 200 including the MAP 210 during step106. Thus, thinner saw blades 222 are shown. The saw blades 222 cutthrough the shield 220, the ground planes 204′ and 206′, as well as thesubstrate 202′. Thus, the MAPs 210, 210′, and 210″ are singulated toindividual packages. Note that although multiple saw blades 222 are,shown, in one embodiment a single saw blade 222 is used multiple timesto make the cuts. Because thinner saw blades 222 are used and becausethe saw blades 222 are positioned such that the shield 220′ stillsubstantially encloses the MAP 210 above the ground planes 204′ and206′, the remaining portion of the electromagnetic shield 220′ is stillcapable of functioning as an electromagnetic radiation shield. Thus, forexample, the shield 220′ may still be sufficiently effective atprotecting the electronics (not explicitly shown) of the MAP 210 from RFradiation.

FIG. 7 depicts the MAP 210 after step 106 is completed. Because the MAP210 was separated in step 106, the other MAPs 210′ and 210″ are notdepicted. However, the MAPs 210′ and 210″ should also have shields (notshown) that are analogous to the shield 220′. As can be seen in FIG. 7,the shield 220′ is integrated into the MAP 210. The shield 220′ stillsubstantially encloses the MAP 210 above the ground planes 204 and 206.The shield 220′ substantially surrounds the portion of the MAP 210 fromthe ground planes 204′ and 206′ and above. Thus, the protective layer208 is substantially surrounded. Thus, the remaining portion of theelectromagnetic shield 220′ is still capable of functioning as anelectromagnetic radiation shield. Thus, for example, the shield 220′ maystill be sufficiently effective at protecting the electronics (notexplicitly shown) of the MAP 210 from RF radiation. In addition, theshield 220′ is formed directly on the MAP 210. In a preferredembodiment, the shield 220′ if fabricated directly on the protectivelayer 208′.

Thus, using the method 100, the electronics package, here a MAP, 210 canbe shielded using an integrated shield 220′. The method 100 may utilizeconventional processes in preparing the MAP 210 for the shield 220′, indepositing the shield 220, and in separating the MAP 210 from remainingMAPs 210′ and 210″. As a result, the shield 220′ is relatively simple tofabricate and incorporate into fabrication of the MAP 210, 210′, and210″. Consequently, custom designing of a shield and custom fabricationof the shield using tools specifically for the shield and the particularelectronics package can be avoided. Inclusion of the shield 220′ in theMAP 210′ may thus be more cost effective. In addition, the shield 220′is preferably integrated into the MAP 210′ and directly on theprotective layer 208′. Consequently, the shield 220′ may notsignificantly increase the size of the MAP 210′. Thus, the shield 220′may also avoid undue increases in size of the MAP 210′ and/or any finalproduct employing the MAP 210′.

A method and system for more easily providing an electromagneticradiation shield for an electronics package are described. The presentinvention has been described in accordance with the embodiments shown,and one of ordinary skill in the art will readily recognize that therecould be variations to the embodiments, and any variations would bewithin the spirit and scope of the present invention. Accordingly, manymodifications may be made by one of ordinary skill in the art withoutdeparting from the spirit and scope of the appended claims.

1. A method comprising: exposing a portion of at least one groundcontact feature in an electronic package, the electronic package locatedon a substrate and having a first portion located above the at least oneground contact feature and a second portion located directly on thesubstrate, wherein the exposing comprises removing the first portion ofthe electronic package form at least one trench above the at least oneground contact feature; depositing electromagnetic radiation shieldmaterial in the at least one trench to form a substantially filled theat least one trench; and depositing additional electromagnetic radiationshield material portion on top of the at least one substantially filledtrench and on top of the second portion of the electronic package toform an integral electromagnetic radiation shield which is electricallyconnected to the at least one ground contact feature.
 2. The method ofclaim 1 wherein the electronic package is a molded array package.
 3. Themethod of claim 1 wherein the first portion of the electronic package isa first portion of a protective layer, and the second portion of theelectronic package is a second portion of the protective layer.
 4. Themethod of claim 3 wherein the protective layer is an over-mold compound.5. The method of claim 4 wherein the removing further comprises sawingthrough the first portion of the protective layer using a first sawblade.
 6. The method of claim 5 wherein the electronic package isphysically coupled to at least one additional electronic package throughat least the substrate.
 7. The method of claim 6 further comprisingseparating the electronic package from the at least one additionalelectronic package wherein a remaining portion of the electromagneticradiation shield substantially encloses a portion of the electronicpackage above the at least one ground contact feature.
 8. The method ofclaim 7 wherein the separating further comprises sawing through thesubstrate and a portion of the electromagnetic radiation shield abovethe at least one ground contact feature using a second saw blade thinnerthan the first saw blade.
 9. The method of claim 1 wherein theelectromagnetic radiation shield is a metallic shield.
 10. The method ofclaim 9 wherein the metallic shield includes at least one of Ni and Fe.11. The method of claim 1 wherein the electromagnetic radiation shieldis a metal-polymer composite.
 12. The method of claim 1 wherein theelectromagnetic radiation shield is a radio frequency shield.
 13. Aproduct produced according to the method of claim
 1. 14. A methodcomprising: providing an electronic package having a substrate, at leastone ground contact feature and a protective layer, wherein theprotective layer has a first portion located above the at least oneground contact feature and a second portion located directly on thesubstrate, wherein the electronic package is physically coupled to atleast one additional electronic package through at least the substrate;exposing a portion of the at least one ground contact feature byremoving the first portion of the protective layer to form at least onetrench above the at least one ground contact feature; depositing anelectromagnetic radiation shield material to substantially cover theelectronic package, to substantially fill the at least one trench with atrench deposit, and to electrically connect the at least one trench tothe at least one ground contact feature, wherein the trench depositforms a sidewall between adjacent electronic components; and separatingthe electronic package from the at least one additional electronicpackage, wherein a remaining portion of the electromagnetic radiationshield substantially encloses a portion of the electronic package abovethe at least one ground contact feature.
 15. The method of claim 14wherein the protective layer comprises an over-mold compound.
 16. Themethod of claim 15 wherein the removing further comprises sawing throughthe first portion of the protective layer using a first saw blade. 17.The method of claim 16 wherein the separating further comprises sawingthrough the substrate and a portion of the electromagnetic radiationshield above the at least one ground contact feature using a second sawblade thinner than the first saw blade.
 18. The method of claim 14wherein the separating step is a singulation process which formssingulated electronic packages.
 19. A product produced according to themethod of claim 14.